2005 Nissan X-TRAIL Pricing and Specs

It sounds like you've tackled the obvious causes of this type of vibration. The dual-mass clutch is a prime candidate and any car with worn engine mounts can vibrate when it's running.

Digging deeper will involve ruling things out in a process of elimination. So, to start that process, does the vibration go away when the vehicle is stationary or only when it's moving? If it's the latter, you could have some kind of transmission or tail-shaft problem. Ot perhaps even a warped brake rotor or seized brake caliper.

But if the vibration is there whenever the engine is running, then you need to start to look at things like the harmonic balancer on the front of the crankshaft and whether the engine itself is actually running smoothly (regardless of where the idle is set). The stepper-motor (which controls the idle) could be faulty leading to the engine flaring between gear changes, and an engine that has a blocked exhaust, dirty air-filter or even worn spark plugs can run roughly. It could even be something like camshaft timing that has jumped a tooth, leading the engine to run poorly and contribute the bad vibrations you're feeling. Also, check the rubber drive belt that powers the alternator and power-steering pump. A worn belt or worn out tensioners and pulleys can also create problems like this. Check the power steering pump itself for signs of its seizing or jamming as it turns.

You’ve possibly drowned something. I doubt it’s the coil, because it seems for your description that the starter is not working. Dry everything in the engine bay that could have been affected by water and see if that cures the problem. You could also try jump-starting it.

I'm not aware of any affordable equipment you could purchase to diagnose problems at home. If you want to save money you could use an independent service agent who would generally charge much less than the dealer.